From 7b3169dfa4ba1b1898d4bdfad6ddabbc9e8a57ed Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Thu, 10 Apr 2025 13:58:35 -0700 Subject: [PATCH] objtool, x86/hweight: Remove ANNOTATE_IGNORE_ALTERNATIVE Since objtool's inception, frame pointer warnings have been manually silenced for __arch_hweight*() to allow those functions' inline asm to avoid using ASM_CALL_CONSTRAINT. The potentially dubious reasoning for that decision over nine years ago was that since !X86_FEATURE_POPCNT is exceedingly rare, it's not worth hurting the code layout for a function call that will never happen on the vast majority of systems. However, those functions actually started using ASM_CALL_CONSTRAINT with the following commit: 194a613088a8 ("x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm()") And rightfully so, as it makes the code correct. ASM_CALL_CONSTRAINT will soon have no effect for non-FP configs anyway. With ASM_CALL_CONSTRAINT in place, ANNOTATE_IGNORE_ALTERNATIVE no longer has a purpose for the hweight functions. Remove it. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Brian Gerst Cc: H. Peter Anvin Cc: Juergen Gross Cc: Kees Cook Cc: Linus Torvalds Link: https://lore.kernel.org/r/e7070dba3278c90f1a836b16157dcd34ccd21e21.1744318586.git.jpoimboe@kernel.org --- arch/x86/include/asm/arch_hweight.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/arch_hweight.h b/arch/x86/include/asm/arch_hweight.h index cbc6157f0b4b..b5982b94bdba 100644 --- a/arch/x86/include/asm/arch_hweight.h +++ b/arch/x86/include/asm/arch_hweight.h @@ -16,8 +16,7 @@ static __always_inline unsigned int __arch_hweight32(unsigned int w) { unsigned int res; - asm_inline (ALTERNATIVE(ANNOTATE_IGNORE_ALTERNATIVE - "call __sw_hweight32", + asm_inline (ALTERNATIVE("call __sw_hweight32", "popcntl %[val], %[cnt]", X86_FEATURE_POPCNT) : [cnt] "=" REG_OUT (res), ASM_CALL_CONSTRAINT : [val] REG_IN (w)); @@ -46,8 +45,7 @@ static __always_inline unsigned long __arch_hweight64(__u64 w) { unsigned long res; - asm_inline (ALTERNATIVE(ANNOTATE_IGNORE_ALTERNATIVE - "call __sw_hweight64", + asm_inline (ALTERNATIVE("call __sw_hweight64", "popcntq %[val], %[cnt]", X86_FEATURE_POPCNT) : [cnt] "=" REG_OUT (res), ASM_CALL_CONSTRAINT : [val] REG_IN (w)); -- 2.25.1